DATABASE DESIGN I - 1DL300

Transcription

1 DATABASE DESIGN I - 1DL300 Autumn 2012 An Introductory Course on Database Systems Uppsala Database Laboratory Department of Information Technology, Uppsala University, Uppsala, Sweden

2 Normalization Example Elmasri/Navathe ch 14 Padron-McCarthy/Risch ch 11 Silvia Stefanova Department of Information Technology Uppsala University, Uppsala, Sweden

3 Outline 1. Normalization Summary Good database design??? Redundancy, Update anomalies, NULL values, spurious tuples Functional dependency (FD), Full functional dependency (FFD) 1 NF 2 NF 3 NF BCNF 2. Publications database example 3. Street database BCNF normalize 4. More exercises on normalization

4 Normalization Summary Good database design??? Redundancy, Update anomalies, NULL values, spurious tuples Functional dependency (FD), Full functional dependency (FFD) 1 NF 2 NF 3 NF BCNF

5 First Normal Form, 1 NF 1NF: Relations should not have multivalued attributes or nested relations. Ssn Ename Pnumber Hours 1234 Smith Wong Normalization: Form new relations for each multivalued attribute or nested relation

6 FD and FFD X Y A P XY X1 Y1 A1 P1 X1Y1 X1 Y2 A1 P2 X1Y2 X2 Y3 A2 P3 X2Y3 FD2 FD1 FD3 FDs : FD1, FD2 FFDs : FD

7 Second Normal Form - 2NF 2NF: A relation is in 2NF if: It is in 1NF Every non-key attribute in the relation is FFD of each candidate key. Employee department pnumber daddress name projects Informational Technology 1234 Polack Sara Project_IT1 Engineering 4567 Ång Erik Project_EE0 Informational Technology 4567 Polack Erik Project _IT2 Normalization: Decompose the relation, set up a new relation for each partial key with its dependent attribute(s)

8 3NF: A relation is in 2NF if: It is in 2NF Third Normal Form - 3NF No non-key attribute in a relation is allowed to be FFD on other non-key attribute. Subdivision subdivision department num_emp Projects Computer Systems Informational Technology 400 Project_IT_CS Systems and Control Informational Technology 400 Project _IT_SysC Electrical Engineering Engineering 1000 Project_ E_EE Normalization: Decompose the relation, set up a new relation including the non-key attribute(s) that is FD on other non-key attribute(s). transitive FD on the primary key

9 Boyce-Codd Normal Form - BCNF BCNF: A relation is in BCNF if: It is in 1NF Every determinant is a candidate key. Teach department course teacher Computing Science Database 1 Sara S Computer Systems Database 1 Sara S Engineering Signals and Systems Peter E Computing Science Database 2 Sven P Normalization: Decompose the relation so that after joining the new relations spurious tuples will not be generated ( lossless join decomposition )

10 Outline 1. Normalization Summary Good database design??? Redundancy, Update anomalies, NULL values, spurious tuples Functional dependency (FD), Full functional dependency (FFD) 1 NF 2 NF 3 NF BCNF 2. Publications database example 3. Street database BCNF normalize 4. More exercises on normalization

11 The Database Publications? Is Publications in 1NF, 2NF or 3NF? Why or why not? How would you normalize it? Area: Scientific area, e.g. Computer Science, Mathematics, Chemistry, etc Paper: Title of a paper. A paper can be published in one journal. Author: Name of the main author of a paper. Journal: Title of a scientific journal where papers can be published. A paper can be published in only one journal. Country: Country of origin for the main author. Language: Publication language for a journal Publications Area Author Paper Journal Country Language

12 Normalization to BCNF? Is Street in BCNF? Why or why not? How would you normalize it? Street street city length zipcode Rydsvägen Linköping Mårdtorpsgatan Linköping Storgatan Linköping Storgatan Gnesta

13 Summary Normalization Redundancy Functional dependency (FD) Full functional dependency (FFD) 1 NF 2 NF 3 NF BCNF